In recent years, a number of new hypotheses related to the etiology of myocardial infarction have been raised. To date, no epidemiologic study has evaluated these potential risk factors and their interrelationships while simultaneously accounting for the role of previously-identified determinants of risk. We therefore propose to conduct a case-control study to examine the interrelationships of alcohol consumption. Lipoproteins, personality, type, diet, vasectomy and other risk factors in the etiology of myocardial infarction (MI). Questionnaire data will be gathered from 750 cases of first MI and an equal of age-, sex-, and town-matched controls randomly from town resident lists. Fasting blood samples from cases and controls will be examined for total cholesterol, cholesterol in high-, low- and very-low-density lipoproteins (HDL, LDL, VLDL) and triglycerides, and vitamin B6. Apolipoproteins and HDL sub-fractions will be determined in a subgroup of cases and controls. The principal analysis will examine the relative risk for MI of moderate alcohol consumers as opposed to non-drinkers when HDL and other established risk factors are controlled in a multiple logistic regression equation. Additional major analyses will examine the role of dietary factors as determinants both of MI and of other risk factors. To quantitate the accuracy of the dietary questionnaire to be used, a validation study will be conducted among a subgroup of controls.